There is no known way to access the command line or install custom firmware or packages on this device without performing hardware modifications to add a SerialPort. The firmware upgrade images are protected with an encrypted hash of the contents, and the encryption algorithm is not known. Therefore there is no way to create modified firmware upgrade images at the moment. Even after you have achieved root access, to flash custom firmware partial images onto the device you need to revert back to the 1.00.04.c firmware to be able to install an unencrypted firmware partial image.

The firmware binary corresponding to the later version 1.00.6 source code has been located at ftp://ftp.linksys.com/downloads/NA/firmware/WRP400_v1%5B1%5D.00.06_fw.bin - this and the newer 2.00.05 firmware has been flashed and will not undo any actions you've taken to UnlockTheConsole or apply the ShadowDataHack. You are also able to downgrade/upgrade from 2.00.05, 1.00.06 and 1.00.04c at any time. However after a 2.00.05 firmware upgrade it seems that the boot loader is replaced with a more limited version of uboot and you can not revert by downgrading.